Rotary Exhaust Valve

ABSTRACT

Disclosed embodiments describe a novel exhaust valve for internal combustion engines. Conventional IC engines, especially two-cycle engines, can allow unspent fuel to exit through the exhaust passage and thus lose power and create unnecessary pollution. A rotary valve for use with internal combustion engines which significantly reduces the amount of unspent fuel leaving the cylinder improves both the power, efficiency and pollution profile of conventional IC engines. The valve is adapted and timed to cover an exhaust exit port of the cylinder during the air intake portion of the piston cycle thereby preventing unspent fuel and air from escaping during a piston controlled cycle.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to co-pending U.S. Application No. 61/670,469 filed on Jul. 11, 2012 and is herein incorporated by reference in its entirety.

TECHNICAL FIELD

The present invention relates generally to an exhaust valve for an internal combustion (IC) engine. More particularly it relates to a rotary exhaust valve for a two-stroke engine which closes the exhaust port to prevent the escape of fresh mixture and pollution related thereto.

BACKGROUND

A two-stroke engine, as compared to a four stroke engine, has the advantages of simple structure, low manufacturing cost, easy maintenance and steady output of horse power. Thus, the two-stroke engine is the power source of choice for many small gas-powered tools etc. However, it also has the disadvantages of higher fuel consumption and higher air pollution.

In the conventional two-stroke engine, a fuel-air mixture is charged into the cylinder. After the compression stroke of the piston the mixture is ignited. The exhaust gases are forced out of the cylinder through an exhaust port by the exhaust stroke of the piston while the fresh fuel-air mixture is added. Unfortunately, a two-stroke uses the incoming charge to push out exhaust from the previous cycle. During the intake portion of the cycle, the exhaust port remains partially open while the piston is completing the exhaust stroke, so some of the fresh fuel-air mixture escapes into the exhaust port. When the engine is operating at large throttle opening, more fuel-air mixture is lost through the exhaust port because of the strong suction in the expansion chamber which is created by expansion of waste gas and its kinetic energy.

The amount of fuel-air mixture lost during operation of a conventional two-stroke engine is significant. This loss of fuel reduces the fuel economy of the engine. The escaped fuel-air mixture also worsens the pollution caused by the engine. The gas which escapes from the cylinder during the final stage of the exhaust stroke contains more hydrocarbons, and has a higher density of burnable gas, than the prior exhaust gas. An engine which reduces the amount of unburned fuel which escapes from the cylinder would have a better fuel economy, and less emission.

SUMMARY

This and other unmet needs of the prior art are met by compounds and methods as described in more detail below.

It is a general object of the present invention to provide an exhaust valve for an internal combustion engine which enables exhaust gases to escape through the exhaust port while keeping the fuel-air mixture within the combustion chamber.

It is a particular object of the present invention to provide a rotary exhaust valve which regulates the flow of exhaust gas in response to the movement of the piston.

A device for controlling the passage of exhaust gases in a two-stroke cycle internal combustion engine, the engine having an air intake passage, an exhaust port leading to an exhaust passage, an exit port leading from the exhaust passage to the ambient, a piston reciprocating in continuous cycles between top and bottom dead center positions in a cylinder, said piston being in mechanical communication with a rotatable crankshaft. The device including a rotary valve member oriented at least partially within the exhaust passage, and actuating means for said valve member to rotate said valve member continuously between an open position and a closed position; the actuating means operating in a timed relation with the crankshaft rotation and piston movement to move the valve member from the closed position toward the open position after the upper edge of the piston passes downward below the upper edge of the exhaust port, and to move the valve member from the open position toward the closed position when the piston is near its bottom position. Furthermore, a device wherein the actuating means rotates the valve member at one half the speed of the piston, and wherein the valve member comprises two symmetrical arms.

The foregoing and other objects are achieved by a rotary exhaust valve for an internal combustion engine which includes a piston assembly, a cylinder assembly including a combustion chamber, a crankcase, a crank apparatus for manipulating the piston assembly. The exhaust valve located among the air passage, the gas-return passage and the exhaust passage includes a valve passage which periodically connects the combustion chamber to the exhaust passage, allowing the exhaust gas to escape from the engine.

A rotary exhaust control valve for two-stroke cycle engines is provided within the exhaust passage of an engine. In an embodiment, the valve is interconnected with the engine crankshaft and rotates between open and close positions in timed relation to the piston movement to delay opening of the exhaust passage during the expansion stroke of the piston and advance closing of the exhaust passage during the compression stroke of the piston. After the exhaust passage is initially opened, the valve rotates towards its open position to allow the expulsion of the stream of exhaust gases passing through the exhaust port.

The valve of the disclosed embodiments provides improved combustion of fuels with more thorough burning of hydrocarbons, less fouling of combustible mixture and better operation of pollution control devices.

BRIEF DESCRIPTION OF THE DRAWINGS

A better understanding of the exemplary embodiments of the invention will be had when reference is made to the accompanying drawings, wherein identical parts are identified with identical reference numerals, and wherein:

FIG. 1 is a cross-section view of an embodiment of an internal combustion engine comprising a novel rotary exhaust valve device.

FIG. 2 is a perspective view of an embodiment of a novel rotary exhaust valve device rotating about an exemplary cylinder.

FIG. 3 is a cross-section view of a multi-cylinder internal combustion engine comprising a novel rotary exhaust device.

FIG. 4 is a cross-section view of an embodiment of a valve drive system multi-cylinder internal combustion engine comprising a novel rotary exhaust device.

DETAILED DESCRIPTION

Two-cycle engines have a reputation for high power to weight ratio due to performing a power-stroke every revolution of the cylinder whereas higher cylinder engines have power-strokes only every other revolution. Thus, a four cylinder would need approximately twice the engine displacement to create the same power generate by a two-stroke model. However, while relatively inexpensive to manufacture and service, two-cycle engines suffer from a poor exhaust profile due to oil and fuel/air mixtures being released during use.

During the operation of a conventional two-cycle engine the exhaust exit opening is controlled by the motion of the cylinder, that is the cylinder blocks both intake and exhaust apertures on the cylinder during the power stroke phase of a cycle. During the down-stroke the exhaust exit opening is exposed first, allowing exhaust fumes to leave the cylinder prior to taking in air and fuel into the cylinder. However, conventional two-cycle engines use the intake air and fuel to push the exhaust remainder out—causing the loss of unspent fuel and fresh intake air along with the exhaust. This is accomplished by making the exhaust apertures higher on the cylinder than the intake apertures. This results in an overlap for the two types of apertures during the cycling of the cylinder. The novel rotary exhaust valve described herein is shaped and timed to minimize the overlap in opening time between the intake and exhaust apertures during operation of the engine.

Conventional two cycle engines use tuned exhaust pipes with internal cone shapes that force escaped fuel/air mixture back into the cylinder in order to increase stroke efficiency after the mixture forces exhaust fumes out. These tuned pipes can be large and clumsy and require one pipe per cylinder. Moreover, the pipes do not return the cylinder to optimal efficiency. Disclosed embodiments of the rotary exhaust valve improve the efficiency of IC engines more than tuned pipes.

Conventional two-cycle engines open the exhaust ports prior to opening the intake ports in order to relieve exhaust pressure prior to intake thus ensuring that the fuel/air mixture pressure is greater than the exhaust gases and thereby the remaining exhaust is forced out of the cylinder by the fuel/air pressure. However, at high RPM the fuel/air mixture is discharged through the exhaust port as well. This is where a tuned pipe system would normally scavenge some of this “lost” fuel/air mixture to increase the power in the cylinder. Disclosed embodiments would close the open exhaust port prior to fuel/air charge leaving the cylinder thereby preserving the power of the cylinder without complicated tuned piping.

A rotary exhaust control valve for two-stroke cycle engines is provided within the exhaust passage of an engine. In an embodiment, the valve is interconnected with the engine crankshaft and rotates between open and close positions in timed relation to the piston movement to delay opening of the exhaust passage during the expansion stroke of the piston and advance closing of the exhaust passage during the compression stroke of the piston. After the exhaust passage is initially opened, the valve rotates towards its open position to allow the expulsion of the stream of exhaust gases passing through the exhaust port.

Turning to the drawings for a better understanding:

FIG. 1 shows a cross-section of an embodiment of an in-line or two-cycle internal combustion engine. The figure shows a novel construction for a two-cycle engine comprising a novel exhaust passage and rotary exhaust valve. The engine includes a cylinder 10 with a piston 20 adapted to travel periodically within the cylinder. The piston is in mechanical communication with a crank 30. During operation fuel is injected into the combustion chamber 40 and is mixed with air from the ambient which enters from the air intake port 50. Combustion in the cylinder generates waste gases which are expelled through the exhaust passage 100. In a conventional engine, the exhaust gases are expelled through an exhaust passage but the passage is substantially open during fuel/air intake—allowing unspent fuel to exit with the exhaust gases and allowing some exhaust gases to reenter the combustion chamber at the bottom of the piston cycle, thus fouling the fuel air mixture in the combustion chamber. During operation, the piston will move between a top position and a bottom position and the motion is translated to other components via the crank.

In an embodiment, the exhaust passage includes a valve for sealing the exhaust passage from the combustion chamber. The exhaust passage comprises an exhaust chamber 110 defined by an exhaust chamber housing 120. The housing includes an exhaust port 130 for releasing exhaust gases from the cylinder into the exhaust passage and an exhaust exit port 140. Within the exhaust passage is a rotary valve member 150. The rotary valve member according to the embodiment shown in FIG. 1 has a body which is made, for example, of a metal, a ceramic or a combination thereof. The body is generally rotationally symmetric with respect to an axis of rotation of the rotary valve. The rotary valve member may comprise two symmetrical and identical arms 160. The arms rotate within the housing in the direction of the arrow shown in the figure. In the embodiment shown in FIG. 1, the arms are concave and curved in the direction of rotation allowing the arms to more effectively close off the exhaust port as the air intake ports are exposed by the cylinder.

In an embodiment the rotation of the valve member is controlled via an actuating means to rotate the valve member continuously between an open position and a closed position. The actuating means operates in a timed relation with the crankshaft rotation and piston movement to move the valve member from a closed position toward the open position after the upper edge of the piston passes downward below the upper edge of the exhaust port, and to move the valve member from the open position toward the closed position when the piston is near its bottom position.

In an embodiment, the valve member creates an imperfect seal with the outer surface of the cylinder when aligned during each half rotation—substantially preventing charged fuel/air mixture from leaving the cylinder after the exhaust gas has been expelled. The rotary valve member rotates about an axis substantially perpendicular to the axis of motion of the piston. The rotary valve member rotates to close off the top of the exhaust exit aperture first during the piston down-stroke and continues to substantially seal apertures during charging of the cylinder. The valve member then rotates away from the apertures during the upstroke of the piston and the opposite end of the valve member rotates into position during the power stroke of the piston. Timing may be accomplished via known devices and methods in the IC engine art such as belt or chain driven timing between the piston movement and the rotation of the valve member. It is clear from the symmetrical arrangement of valve member arms that the valve member need only rotate at half the piston speed in order to effectively cover the exhaust apertures during each piston revolution.

Disclosed embodiments describe a valve adapted to counterbalance its own rotary movement and that is timed at half the speed of the cylinder. However, those skilled in the art will recognize that different numbers of blades in the rotary valve member may allow the valve to operate at other than half engine speed. Embodiments of the rotary exhaust valve described herein may be timed using conventional belt or chain timing thus allowing the novel rotary valve to operate without mechanical valve trains that might drain power from the engine.

FIG. 2 shows an embodiment of a rotary valve member adjacent an internal combustion engine cylinder 10. The rotary valve member 250 is comprised of two counterbalanced arms 260 about a valve shaft 251. The member is adapted for rotational operation within the chamber defined by the exhaust passage housing (not shown). Disclosed embodiments describe a valve adapted to counterbalance its own rotary movement and that is timed at half the speed of the cylinder. However, those skilled in the art will recognize that different numbers of blades in the rotary valve member may allow the valve to operate at other than half engine speed. Embodiments of the rotary exhaust valve described herein may be timed using conventional belt or chain timing thus allowing the novel rotary valve to operate without mechanical valve trains that might drain power from the engine.

The rotary valve member according to the embodiment shown in FIG. 2 has a body which is made, for example, of a metal, a ceramic or a combination thereof. The body is generally rotationally symmetric with respect to an axis of rotation of the rotary valve. The rotary valve member may comprise two symmetrical and identical arms 260. The arms rotate within the housing in the direction of the arrow shown in the figure. The arms are curved and positioned to register with the exhaust ports 230 of the cylinder. As can be seen in the drawing, the distal surface 270 of each arm is curved to accommodate the rounded outer surface of the cylinder. The distal surface is sized and shaped to cover the exhaust port(s) completely during engagement with the cylinder on each rotation. The curvature of the distal surface allows for tight but not totally sealed registration between the cylinder and the valve member.

In an embodiment, the valve member creates an imperfect seal with the outer surface of the cylinder when aligned during each half rotation—substantially preventing charged fuel/air mixture from leaving the cylinder after the exhaust gas has been expelled. The rotary valve member rotates about an axis substantially perpendicular to the axis of motion of the piston. During operation, the rotary valve member rotates a first arm to close off the top of the exhaust exit aperture first during the piston down-stroke and continues to substantially seal apertures during charging of the cylinder. The arm then rotates away from the apertures during the upstroke of the piston and the opposite arm of the valve member rotates into position during the power stroke of the piston. Timing may be accomplished via known devices and methods in the IC engine art such as belt or chain driven timing between the piston movement and the rotation of the valve member. It is clear from the symmetrical arrangement of valve member arms that the valve member need only rotate at half the piston speed in order to effectively cover the exhaust apertures during each piston revolution.

In an embodiment the rotation of the valve member is controlled via an actuating means to rotate the valve member continuously between an open position and a closed position. The actuating means operates in a timed relation with the crankshaft rotation and piston movement to move the valve member from a closed position toward the open position after the upper edge of the piston passes downward below the upper edge of the exhaust port, and to move the valve member from the open position toward the closed position when the piston is near its bottom position.

As can be seen in FIG. 2, the arm need not be comprised of a solid piece of material but may be comprised of a hollow member. In an embodiment, the arm is curved in the direction of rotation about the valve shaft. The open or hollow arm allows the exhaust gases to freely leave through the exhaust passage. In an alternative embodiment, the arm may comprise a substantially solid piece. Many different arrangements of the arm are possible so long as the exhaust is not impeded from leaving the exhaust passage during operation of the valve. In an alternative embodiment, the valve member includes solid arms and the distal surface of each arm is curved accommodate the rounded outer surface of the cylinder. In an embodiment, the valve member creates an imperfect seal with the outer surface of the cylinder when aligned during each half rotation —substantially preventing charged fuel/air mixture from leaving the cylinder after the exhaust gas has been expelled.

Each of the arms has a leading edge 261 and a trailing edge 262. In an embodiment, the leading edge and trailing edge are curved with respect to the direction of rotation. Each of the edges define a curved concave surface with respect to the direction of rotation of the valve. In the embodiment shown in FIG. 2 the leading edge is more curved than the trailing edge the result being that the distal surface of the valve member's arms is wider than the proximal end—the end nearer the center of rotation of the valve.

Brakes are often the part of racing vehicles that break down fastest due to the high stress put on the brake system. This is especially true in an endurance racing environment. One possible solution to the high cost and time of brake maintenance is to use engine braking or jake braking. A variable exhaust control could be used to close exhaust ports in conjunction with a fuel shut-off mechanism to create an engine brake in order to reduce brake change and failure without harming the engine.

In an alternative embodiment, a rotary exhaust valve is timed via an actuating means and with a fuel shut-off to enable engine braking. The rotary exhaust valve may be timed to rotate in conjunction with the fuel system, and block the exhaust opening on the cylinder while the fuel system ceases to provide fuel to the cylinder. By preventing the exhaust from leaving the cylinder, the cylinder will not have sufficient fuel air pressure to fire and power will thus be eliminated. The engine shut-off due to the exhaust and fuel systems working in concert will reduce the strain on the braking system and prolong the lifespan of brake parts.

FIG. 3 shows a cross-section of an embodiment of an internal combustion engine. The figure shows a novel construction for an engine comprising a novel exhaust passage and rotary exhaust valve. The engine includes a cylinder 10 with a piston 20 adapted to travel periodically within the cylinder, an oil sump 70 below the crank and a super charger 80 positioned above the engine. The piston is in mechanical communication with a crank. During operation fuel is injected into the combustion chamber and is mixed with air from the ambient which enters from the air intake port 50. Combustion in the cylinder generates waste gases which are expelled through the exhaust passage 100. In a conventional engine, the exhaust gases are expelled through an exhaust passage but the passage is substantially open during fuel/air intake—allowing unspent fuel to exit with the exhaust gases and allowing some exhaust gases to reenter the combustion chamber at the bottom of the piston cycle, thus fouling the fuel air mixture in the combustion chamber. During operation, the piston will move between a top position and a bottom position and the motion is translated to other components via the crank.

In an embodiment, the exhaust passage includes a valve for sealing the exhaust passage from the combustion chamber. The exhaust passage comprises an exhaust chamber 110 defined by an exhaust chamber housing 120. The housing includes an exhaust port 130 for releasing exhaust gases from the cylinder into the exhaust passage and an exhaust exit port 140. Within the exhaust passage is a rotary valve member 150. The rotary valve member according to the embodiment shown in FIG. 3 has a body which is made, for example, of a metal, a ceramic or a combination thereof. The body is generally rotationally symmetric with respect to an axis of rotation of the rotary valve. The rotary valve member may comprise two symmetrical and identical arms 160. The arms rotate within the housing in the direction of the arrow shown in the figure. In the embodiment shown in FIG. 3, the arms are curved in the direction of rotation allowing the arms to more effectively close off the exhaust port as the air intake ports are exposed by the cylinder. Optionally, the distal edge of the rotary member further comprises a plate 171 for increasing contact with the exhaust ports.

In an embodiment the rotation of the valve member is controlled via an actuating means to rotate the valve member continuously between an open position and a closed position. The actuating means operates in a timed relation with the crankshaft rotation and piston movement to move the valve member from a closed position toward the open position after the upper edge of the piston passes downward below the upper edge of the exhaust port, and to move the valve member from the open position toward the closed position when the piston is near its bottom position.

In an embodiment, the valve member creates an imperfect seal with the outer surface of the cylinder when aligned during each half rotation—substantially preventing charged fuel/air mixture from leaving the cylinder after the exhaust gas has been expelled. The rotary valve member rotates about an axis substantially perpendicular to the axis of motion of the piston. The rotary valve member rotates to close off the top of the exhaust exit aperture first during the piston down-stroke and continues to substantially seal apertures during charging of the cylinder. The valve member then rotates away from the apertures during the upstroke of the piston and the opposite end of the valve member rotates into position during the power stroke of the piston. Timing may be accomplished via known devices and methods in the IC engine art such as belt or chain driven timing between the piston movement and the rotation of the valve member. It is clear from the symmetrical arrangement of valve member arms that the valve member need only rotate at half the piston speed in order to effectively cover the exhaust apertures during each piston revolution.

Those of skill in the art will recognize that while this embodiment includes multiple pistons, exhaust ports and exhaust control mechanisms. The general concept is the same and the timing of the system will allow the exhaust control systems to operate in concert in much the same manner as the single exhaust embodiments shown above.

FIG. 4 is a cross-section of the belt/timing portion of the embodiment of the engine shown in FIG. 3. In this figure, the valve drive system is shown. The crank drive 35 is shown in communication with belts 36 driving valves. In this embodiment, the valves are timed at ½ engine RPM.

The terms “a” and “an” and “the” and similar references used in the context of describing the disclosed embodiments (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context.

Recitation of ranges of values herein is merely intended to serve as a shorthand method of referring individually to each separate value falling within the range. Unless otherwise indicated herein, each individual value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g. “such as”) provided herein is intended merely to better illuminate the disclosed embodiments and does not pose a limitation on the scope of the disclosed embodiments unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element essential to the practice of the disclosed embodiments or any variants thereof.

Groupings of alternative elements or embodiments disclosed herein are not to be construed as limitations. Each group member may be referred to and claimed individually or in any combination with other members of the group or other elements found herein. It is anticipated that one or more members of a group may be included in, or deleted from, a group for reasons of convenience and/or patentability

Preferred embodiments of this invention are described herein, including the best mode known to the inventors for carrying out the invention(s). Of course, variations on the disclosed embodiments will become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventors expect skilled artisans to employ such variations as appropriate, and the inventors intend for the invention(s) to be practiced otherwise than specifically described herein. Accordingly, this disclosure includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above described elements in all possible variations thereof is encompassed by the disclosed embodiments unless otherwise indicated herein or otherwise clearly contradicted by context.

Having shown and described an embodiment of the invention, those skilled in the art will realize that many variations and modifications may be made to affect the described invention and still be within the scope of the claimed invention. Additionally, many of the elements indicated above may be altered or replaced by different elements which will provide the same result and fall within the spirit of the claimed invention. It is the intention, therefore, to limit the invention only as indicated by the scope of the claims. 

What is claimed is:
 1. A device for controlling the passage of exhaust gases in an internal combustion engine, the engine having an air intake passage, an exhaust port leading to an exhaust passage, an exit port leading from the exhaust passage to the ambient, a piston reciprocating in continuous cycles between top and bottom dead center positions in a cylinder, said piston being in mechanical communication with a rotatable crankshaft; the device comprising: a rotary valve member oriented at least partially within the exhaust passage; actuating means for the valve member to rotate the valve member continuously between an open position and a closed position; the actuating means operating in a timed relation with the crankshaft rotation and piston movement to move the valve member from the closed position toward the open position after the upper edge of the piston passes downward below the upper edge of the exhaust port, and to move the valve member from the open position toward the closed position when the piston is near its bottom position.
 2. The device of claim 1 wherein the actuating means rotates the valve member at one half the speed of the piston.
 3. The device of claim 1 wherein the valve member comprises two symmetrical arms. 